Frame for a backpack



FIG. 1 is a top view of a frame for a backpack showing my new design;

FIG. 2 is a bottom view thereof;

FIG. 3 is a front view thereof;

FIG. 4 is a side view thereof;

FIG. 5 is a rear view thereof; and,

FIG. 6 is a front perspective view thereof. 

CLAIM The ornamental design for a frame for a backpack, as shown and described. 